diff options
| author | Uwe Kleine-König <u.kleine-koenig@pengutronix.de> | 2019-08-24 17:37:07 +0200 |
|---|---|---|
| committer | Thierry Reding <thierry.reding@gmail.com> | 2019-09-21 03:25:10 +0200 |
| commit | 71523d1812aca61e32e742e87ec064e3d8c615e1 (patch) | |
| tree | 20491f0323c9b71d0628741824c4dcf992e22363 /include | |
| parent | pwm: fsl-ftm: Don't update the state for the caller of pwm_apply_state() (diff) | |
| download | linux-71523d1812aca61e32e742e87ec064e3d8c615e1.tar.xz linux-71523d1812aca61e32e742e87ec064e3d8c615e1.zip | |
pwm: Ensure pwm_apply_state() doesn't modify the state argument
It is surprising for a PWM consumer when the variable holding the
requested state is modified by pwm_apply_state(). Consider for example a
driver doing:
#define PERIOD 5000000
#define DUTY_LITTLE 10
...
struct pwm_state state = {
.period = PERIOD,
.duty_cycle = DUTY_LITTLE,
.polarity = PWM_POLARITY_NORMAL,
.enabled = true,
};
pwm_apply_state(mypwm, &state);
...
state.duty_cycle = PERIOD / 2;
pwm_apply_state(mypwm, &state);
For sure the second call to pwm_apply_state() should still have
state.period = PERIOD and not something the hardware driver chose for a
reason that doesn't necessarily apply to the second call.
So declare the state argument as a pointer to a const type and adapt all
drivers' .apply callbacks.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/pwm.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/pwm.h b/include/linux/pwm.h index 24632a7a7d11..b2c9c460947d 100644 --- a/include/linux/pwm.h +++ b/include/linux/pwm.h @@ -262,7 +262,7 @@ struct pwm_ops { int (*capture)(struct pwm_chip *chip, struct pwm_device *pwm, struct pwm_capture *result, unsigned long timeout); int (*apply)(struct pwm_chip *chip, struct pwm_device *pwm, - struct pwm_state *state); + const struct pwm_state *state); void (*get_state)(struct pwm_chip *chip, struct pwm_device *pwm, struct pwm_state *state); struct module *owner; @@ -316,7 +316,7 @@ struct pwm_capture { /* PWM user APIs */ struct pwm_device *pwm_request(int pwm_id, const char *label); void pwm_free(struct pwm_device *pwm); -int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state); +int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state); int pwm_adjust_config(struct pwm_device *pwm); /** |